How popular is Harriot?

Harriot is an unusual given name for women but a somewhat prominent surname for both adults and children (#124109 out of 150436, Top 82%). (2000 U.S. Demographics)

Which version is better?

with its source form and related girl names. Prominent variation forms of Harriot (not ranked) are Harriet(#1314 from recent data) and Harriett. Other forms, like Harriotte, are uncommon. Adoption of these relations of Harriot reached its most widespread a century ago (average #142) and is now significantly less, with forms like Harriett becoming less fashionable. (Top Baby Names, 2015)